The present invention relates to electrically insulated silicon structures and producing methods therefor. A silicon substrate used in the present invention may be pure without impurity, or may include an impurity. It is important for the present invention to be applied to a crystalline structure as a silicon crystal.
JAPANESE JOURNAL OF APPLIED PHYSICS, VOL. 27, NO. 9, SEPTEMBER, 1988, pp. L1778-L1779 by Shimizu et al. and Extended Abstracts (The 37th Spring Meeting, 1990); The Japan Society of Applied Physics and Related Societies No. 2, 30a-SB-5, page 613 by Iwameji et al. disclose fabrications of fine silicon structures.
In these disclosures, as shown in FIGS. 3A and 3B, a crystal face of (111) crystal orientation which is the most anti-etching or etching-resistant face in the silicon is utilized for forming an outer surface of the silicon structure. When a silicon substrate 10 on which an anti-etching pattern layer 12 is formed through lithography is etched by ethylene-diamine solution or potassium hydroxide solution or the like, side walls 13 extending along the crystal face of the (111) crystal orientation of the silicon remain to form a projection 40 with a trapezoid cross-section.